# interFoam nozzle simulation diverges

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 May 15, 2020, 10:53 interFoam nozzle simulation diverges #1 New Member   Liz Join Date: Apr 2020 Location: Germany Posts: 10 Rep Power: 6 Hello everybody, I've been having some trouble trying to simulate the flow through a nozzle. The nozzle is located inside a box, which outlet is defined on the upper side of the box. At the nozzle's outlet I've made some mesh refinement: That's what it looks like a cone (see pictures). Regardless of the time step, alpha is after 2-3 iteration smaller than 0 and bigger than 1. I guess, that's why the simulation at some point diverges. I've tried to change the fvscheme, fvsolution and boundary condition but nothing seems to help. The output from checkMesh was ok. These are one of the first iterations and the one when everything starts to go really wrong: Code: ```Courant Number mean: 0.001011663 max: 33.73018 Interface Courant Number mean: 3.233757e-06 max: 1.547393 Time = 0.0006 PIMPLE: iteration 1 smoothSolver: Solving for alpha.water, Initial residual = 0.002851213, Final residual = 5.817432e-09, No Iterations 3 Phase-1 volume fraction = 4.606276e-06 Min(alpha.water) = -8.110569e-37 Max(alpha.water) = 1 MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water Phase-1 volume fraction = 4.606276e-06 Min(alpha.water) = -5.658737e-29 Max(alpha.water) = 1 smoothSolver: Solving for Ux, Initial residual = 0.2224137, Final residual = 5.36794e-08, No Iterations 15 smoothSolver: Solving for Uy, Initial residual = 0.05766709, Final residual = 8.711863e-08, No Iterations 14 smoothSolver: Solving for Uz, Initial residual = 0.005021781, Final residual = 6.344698e-08, No Iterations 11 GAMG: Solving for p_rgh, Initial residual = 0.0002026823, Final residual = 1.482498e-06, No Iterations 65 GAMG: Solving for p_rgh, Initial residual = 8.477441e-06, Final residual = 9.10022e-08, No Iterations 3 time step continuity errors : sum local = 3.456393e-08, global = 1.273059e-08, cumulative = 1.984811e-08 GAMG: Solving for p_rgh, Initial residual = 1.145649e-05, Final residual = 9.459702e-08, No Iterations 68 GAMG: Solving for p_rgh, Initial residual = 3.933028e-06, Final residual = 5.324668e-08, No Iterations 2 time step continuity errors : sum local = 1.621167e-08, global = 2.118172e-09, cumulative = 2.196628e-08 GAMG: Solving for p_rgh, Initial residual = 3.024072e-06, Final residual = 4.312977e-08, No Iterations 66 GAMG: Solving for p_rgh, Initial residual = 9.835354e-07, Final residual = 4.512249e-08, No Iterations 1 time step continuity errors : sum local = 1.245904e-08, global = 1.925232e-09, cumulative = 2.389151e-08 smoothSolver: Solving for epsilon, Initial residual = 0.03281331, Final residual = 4.027295e-08, No Iterations 11 bounding epsilon, min: -11.98792 max: 64604.16 average: 3.231076 smoothSolver: Solving for k, Initial residual = 0.1275502, Final residual = 8.044356e-08, No Iterations 12 ExecutionTime = 106.59 s ClockTime = 110 s Courant Number mean: 0.01542766 max: 4305.785 Interface Courant Number mean: 0.001508509 max: 4305.785 Time = 0.2244 PIMPLE: iteration 1 smoothSolver: Solving for alpha.water, Initial residual = 0.0003461995, Final residual = 9.638341e-09, No Iterations 67 Phase-1 volume fraction = 0.002594258 Min(alpha.water) = -9.943067e-05 Max(alpha.water) = 1.000747 MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water Phase-1 volume fraction = 0.002594258 Min(alpha.water) = -14.12184 Max(alpha.water) = 14.91034 smoothSolver: Solving for Ux, Initial residual = 0.28712, Final residual = 6.795894e-08, No Iterations 22 smoothSolver: Solving for Uy, Initial residual = 0.3240182, Final residual = 7.216942e-08, No Iterations 21 smoothSolver: Solving for Uz, Initial residual = 0.05525987, Final residual = 5.901969e-08, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 6.635285e-05, Final residual = 5.24964e-07, No Iterations 257 GAMG: Solving for p_rgh, Initial residual = 6.930181e-08, Final residual = 6.930181e-08, No Iterations 0 time step continuity errors : sum local = 0.002720822, global = -2.326503e-06, cumulative = -4.235363e-06 GAMG: Solving for p_rgh, Initial residual = 1.175393e-07, Final residual = 2.416806e-08, No Iterations 1 GAMG: Solving for p_rgh, Initial residual = 3.561633e-08, Final residual = 3.561633e-08, No Iterations 0 time step continuity errors : sum local = 0.001397755, global = -1.039455e-07, cumulative = -4.339308e-06 GAMG: Solving for p_rgh, Initial residual = 6.183298e-08, Final residual = 6.183298e-08, No Iterations 0 GAMG: Solving for p_rgh, Initial residual = 6.183298e-08, Final residual = 6.183298e-08, No Iterations 0 time step continuity errors : sum local = 0.002426621, global = 9.706378e-08, cumulative = -4.242245e-06 smoothSolver: Solving for epsilon, Initial residual = 0.03335731, Final residual = 5.528391e-08, No Iterations 10 bounding epsilon, min: -3.069506e+08 max: 2.650014e+14 average: 1.599839e+09 smoothSolver: Solving for k, Initial residual = 0.1363255, Final residual = 8.208013e-08, No Iterations 12 bounding k, min: -20.41971 max: 2.017263e+08 average: 4944.138 ExecutionTime = 18425.42 s ClockTime = 18737 s``` I've also attached here the case files and the complete log file. On the pictures you can also see an example for alpha at 0.1 ms, where the negative values and the ones greater than 1 are shown. Am I doing something wrong here? I'm grateful for any help! box_nozzle.png 01ms_alpha.jpg 01ms_alpha_smaller_bigger_than.jpg NOZZLE_CASE.zip mesh_nozzle.jpg

 Tags alpha.water, interfoam, unbound variable, vof method, vof model